refactor: remove knowledge base references from AI agent model and related services

- Removed KnowledgeIDs from CreateAIAgentRequest and AIAgentResponse.
- Updated buildAIAgentResponseWithLocale to eliminate knowledge base name retrieval.
- Refactored AI agent repository and service to remove knowledge base handling.
- Adjusted dashboard service to no longer track AI agents without knowledge bases.
- Modified knowledge base service to check for workflow references instead of AI agent references.
- Updated frontend components to remove knowledge base selection and display.
- Enhanced workflow validation to ensure knowledge retrieve nodes have associated knowledge bases.

internal/ai/workflow/registry/registry_test.go

@@ -23,8 +23,8 @@ func TestDefaultRegistryExposesStartOutputs(t *testing.T) {
 	if !hasVariable(spec.OutputSchema, "userMessage", VariableTypeString) {
 		t.Fatalf("expected start output userMessage:string, got %#v", spec.OutputSchema)
 	}
-	if !hasVariable(spec.OutputSchema, "knowledgeBaseIds", VariableTypeIntegerArray) {
-		t.Fatalf("expected start output knowledgeBaseIds:array<int>, got %#v", spec.OutputSchema)
+	if hasVariableName(spec.OutputSchema, "knowledgeBaseIds") {
+		t.Fatalf("did not expect start output knowledgeBaseIds after knowledge binding moved to retrieve node, got %#v", spec.OutputSchema)
 	}
 }
 
@@ -39,6 +39,9 @@ func TestDefaultRegistryExposesKnowledgeRetrieveInputsAndOutputs(t *testing.T) {
 	if !hasVariable(spec.OutputSchema, "items", VariableTypeObjectArray) {
 		t.Fatalf("expected knowledge_retrieve output items:array<object>, got %#v", spec.OutputSchema)
 	}
+	if spec.ConfigSchema == nil {
+		t.Fatalf("expected knowledge_retrieve config schema")
+	}
 }
 
 func TestDefaultRegistryExposesSendReplyRequiredInput(t *testing.T) {